極狐阿爾法 S 華為 HI 版產線驗證車今日正式下線
阿新 • • 發佈:2021-05-26
第一個Mybatis程式
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思路:搭建環境—>匯入Mybatis—>編寫程式碼—>測試!
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2.1、搭建環境
2.1.1、搭建資料庫
CREATE TABLE `Users`( `id` INT(10) NOT NULL, `name` VARCHAR(30) NOT NULL, `pwd` VARCHAR(30) NOT NULL, PRIMARY KEY(`id`) )ENGINE=INNODB DEFAULT CHARSET=utf8; INSERT INTO `Users`(`id`,`name`,`pwd`) VALUES (1,'王五','123456'), (2,'張三','123423'), (3,'李四','123456');
2.1.2、新建專案
- 新建了一個普通的 maven 專案
- 刪除 src 目錄
- 匯入maven依賴
<!--匯入依賴--> <dependencies> <!--mysql驅動--> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.22</version> </dependency> <!--mybatis --> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.5.3</version> </dependency> <!--junit --> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> </dependency>
2.2、建立一個模組
2.2.1、編寫mybatis的核心配置檔案
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <!--configuration--> <configuration> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql://localhost:3306/shop?useUnicode=true&characterEncoding=utf8&useSSL=true&serverTimezone=Asia/Shanghai"/> <property name="username" value="root"/> <property name="password" value="123456"/> </dataSource> </environment> </environments> <mappers> <mapper resource="org/mybatis/example/BlogMapper.xml"/> </mappers> </configuration>
2.2.2、編寫mybatis工具類
//sqlSessionFactory --> sqlSession
public class MybatisUtils {
private static SqlSessionFactory sqlSessionFactory;
static{
try{
//使用Mybatis第一步:獲取aqlSessionFactory物件
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
//既然有了 SqlSessionFactory,顧名思義,我們可以從中獲得 SqlSession 的例項。
// SqlSession 提供了在資料庫執行 SQL 命令所需的所有方法。
// 你可以通過 SqlSession 例項來直接執行已對映的 SQL 語句。
public static SqlSession getSqlSession(){
return sqlSessionFactory.openSession();
}
}
2.3、編寫程式碼
2.3.1、實體類
public class User {
private int id;
private String name;
private String pwd;
public User() {
}
public User(int id, String name, String pwd) {
this.id = id;
this.name = name;
this.pwd = pwd;
}
public int getId() {
return id;
}
public String getName() {
return name;
}
public String getPwd() {
return pwd;
}
public void setId(int id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
public void setPwd(String pwd) {
this.pwd = pwd;
}
}
2.3.2、Dao介面
public interface UserDao {
List<User> getUserList();
}
2.3.3、介面實現類
由原來的UserDaoImpl轉變為一個Mapper配置檔案
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.saxon.dao.UseDao">
<select id="getUserList" resultType="com.saxon.pojo.User">
select * from users
</select>
</mapper>
測試
注意一點:
org.apache.ibatis.binding.BindingException: Type interface com.chen.dao.UseDao is not known to the MapperRegistry.
<mappers> <mapper resource="com/saxon/dao/UserMapper.xml"/></mappers>
public class UserDaoTest extends TestCase {
@Test
public void test(){
//第一步:獲得SqlSession物件
SqlSession sqlSession = MybatisUtils.getSqlSession();
try {
//執行sql
//方式一:getMapper
UserDao userDao = sqlSession.getMapper(UserDao.class);
List<User> userList = userDao.getUserList();
for (User user : userList) {
System.out.println(user);
}
}finally {
//關閉SqlSession
sqlSession.close();
}
}
}
2.4.1、junit測試
- 資源過濾問題 在pom.xml新增下面配置
<build>
<resources>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
</resources>
</build>
可能會遇到的問題:
- 配置檔案沒有註冊
- 繫結介面錯誤。
- 方法名不對
- 返回型別不對
- Maven匯出資源問題